Within packaging technology where a package is formed from a packaging material, it is known to supply the packaging material as individual sheets cut from a web before filling or as a web to be formed into a tube during the process of filling, sealing and forming a packaging container. Guiding marks, e.g. for optical reading has been provided to carry operation-related information to guide operations when said individual sheets or web is formed through folding and sealing to the packaging container. Such optical guiding marks are sometimes referred to as register marks (“bar codes”). The register mark for optical reading is provided during printing of the packing material, where e.g. decoration or product information is printed on the packaging material. A problem with such register marks is that they consume a non-negligible area of what becomes the exterior of the packaging container. Attempts have been made to reduce such undesirably consumed exterior surface by reducing the physical size of the mark. However since reducing the physical size is restricted to a lower critical limit size below which the mark is too small to be detectable with at least a minimum of required accuracy by means of available optical means.
EP 705759 A1 discloses the use of a magnetic mark in packaging material to store package relevant information. However, the magnetic marks do not allow precise adjustment of the packaging material in the filling machine, nor the transfer of substantial amount of data from the production site of the packaging material into the filling machine and beyond.
Objective
An objective of the invention is therefore to provide an improved package based on a web of packaging material with magnetic marks.
A packaging material for such improved package is provided in the form of a web or individual blanks for reforming into packages according to known form/fill/seal principles to obtain formed, filled and sealed packaging containers for transport and handling of food. Well known examples of such packaging containers are Tetra Brik, Tetra Rex, Tetra Fino, Tetra Recart, Tetra Top (all of which are registered trademarks assigned to Tetra Pak), see PACKAGING'S ENCYCLOPEDIA 1987, pp 93 ff. for a more detailed information of shape and dimension of a typical example of a commercial Tetra Brik package. A common feature of most of packaging materials for these commercial packaging containers is that they comprise a rigid, but foldable base layer of paperboard and outer liquid-tight films or coatings of polyolefin, usually polyethylene on both sides of said base layer. In cases where the finished package is to be used for especially oxygen sensitive food, such as juice, wine, edible oil, the packaging material is supplemented with at least one additional layer of a material having the desired barrier properties to gases, in particular oxygen. One preferred such barrier layer is an aluminium foil (Al foil) through which the packaging material can be sealed by means of induction heating which is a rapid efficient heat sealing technique.
In order to facilitate forming through folding of the packaging material, said packaging material can be provided with a pattern of crease lines along which the material is intended to be folded when it is reformed into finished packaging containers. The crease lines are created during the production of the packaging material. It is also preferred to provide the packaging material with a unique print of aesthetic and/or informative character (so called décor) to be visually displayed on the outside of the package manufactured thereof.
A packaging material to be used for a package for transport and handling of food must of course be composed and configured so as to provide the best possible chemical as well as mechanical protection to the food contained therein, and a further demand on the laminate is that it shall enable manufacturing of consumer friendly packaging containers which are easy to open without the need to use an extra tool to get access to its content. The packaging material is therefore usually provided with an integral opening device, such as a pre-cut hole through which the package is intended to be emptied.
One conventional method for manufacturing a packaging material as described above includes along a first integrated converting line the steps of: passing a web of paperboard to and through a printing station in which a desired pattern of print of aesthetic and/or informative character is repeatedly applied on one surface of the paperboard, i.e on the surface which is intended to be facing outwardly when the packaging material subsequently is reformed into packages. The so printed web is passed forward to a creasing station immediately following or linked to printing station so as to provide the web with a repeatedly applied pattern of crease lines in alignment with the already applied pattern of print.
As suggested above, it often happens that the web is provided also with a pre-made opening device including a pre-cut hole through which the content of a filled packages is intended to be emptied. Such a hole can be cut either by means of a mechanical tool or by means of laser cutting. Mechanical cutting is usually made in an operation very close to the creasing operation, while laser cutting can be carried out in an operation both timely and physically separated from said creasing operation. Irrespective of manner of cutting, it is important that the cut hole is positioned in alignment with the pattern of crease lines so as to obtain a packaging container of high quality both in view of functionality and appearance.
The web is then rolled and moved to a second integrated converting line comprising several coating or lamination stations where the web in a first coating station is provided with an outer layer of polyolefin which is applied through extrusion coating on the printed surface of the paperboard. The web is passed further to a second coating or lamination station in which the opposite surface of the paperboard, i.e the surface which is intended to be facing inwardly when the packaging material is formed into packaging containers, is coated with an outer layer of polyolefin through extrusion coating. In case the packaging material is intended for packages for oxygen sensitive food, such as juice, wine, edible oil etc, a gas barrier layer, usually an aluminium foil (Al foil) is first laminated to said opposite surface before the outer layer of polyolefin is applied so as to prevent contact between the foil and the food to be included in the packaging container. The so coated and laminated web is finally rolled and moved to a third integral converting line for inspection, doctoring, slitting and similar mechanical operations on the web to bring the web into an acceptable condition for reforming into filled and sealed packages.
The present invention is based on the understanding that magnetic marking can be provided on a packaging material. In the present disclosure, it is suggested that one or more detectable magnetisable portions per intended package to be formed from the web is provided on the web, wherein the detectable magnetisable portions comprises magnetisable particles such that magnetic marking is enabled.
According to a first aspect, there is provided a packaging material comprising a plurality of magnetisable portions thereon comprising at least one detectable magnetisable portion per package to be formed from the packaging material, wherein at least one of the magnetisable portions provides a first magnetic mark carrying a magnetic field pattern.
The magnetic pattern of the first magnetic mark may be representing complex data. The material may define a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, and a longitudinal direction perpendicular to the transversal direction, wherein the magnetisable portion providing the first magnetic mark may comprise a strip essentially along the longitudinal direction of the web. The complex data may hold information from which the material can be uniquely identified, preferably information from which a part of the material where the magnetisable portion providing the magnetic mark is present can be uniquely identified. The complex data may be represented as a modulating scheme of the magnetic field of the magnetic pattern, wherein the modulating scheme may comprise any of a group comprising frequency shift keying, amplitude shift keying, quadrature amplitude modulation, and pulse width modulation. Preferably, said complex data are represented as a modulating scheme comprising phase shift keying which presently is considered to be the most robust and accurate one for the intended purposes.
Said first magnetic mark is preferably provided as early as possible in a converting line used to manufacture a packaging material to enable complete and individual recording of any events occurring along the whole converting line. Therefore said magnetic mark is applied and individually energised already in connection with a printing operation which usually is carried out as the first operation on a web of paperboard. Preferably, said first mark is printed directly on one surface of the paperboard in a manner so as to obtain at least one such mark per package to be produced from said web, wherein said at least one mark is printed like a stripe extending repeatedly interrupted in the longitudinal direction of the web.
In one aspect, said first individually coded magnetic mark can be used for traceability purposes. To this end magnetic detecting means (detector or reader) are provided along the physically separated, integral converting lines (see above) in communication with each operational station with the intention to detect passages of consecutive codes or ID so as to be able to record any detected operation faults or other events in close linkage to the respective codes in a database accessible for tracing. Not only faults, but also operational parameters, such as temperatures, coating amounts of polyolefin can be recorded and used for setting forming parameters (sealing temperatures for example) in a filling machine to save time for an operator. In a similar manner the database can also be used to save information about process conditions used to treat a product before filling etc. A specific application of the ID coding of the dynamic mark is in connection with finishing operations on the web, such as doctoring, where the mark can be used as control means to stop the web exactly where a converting-related fault has been recorded.
At least one of the magnetisable portions may provide a second magnetic mark carrying a magnetic field pattern aligned with at least one preparation feature for enhancing finishing of packages. The preparation feature may comprise any of a group comprising crease lines, openings, perforations, package boundary or sealing, beginning of web, end of web, positioning of optical mark, print for package outside. A distance between an area of a preparation feature and its aligned magnetic field mark may be at least 2 mm, preferably at least 5 mm, preferably at least 7 mm, preferably at least 10 mm.
At least one of the detectable magnetisable portions for each package to be formed may be positioned not more than 20%, preferably between 5 and 15% of the width of the material to form a package from a longitudinal edge of the material to form the package. The reason is that a conventional filling machine used to manufacture a packaging container according to forming/filling/sealing principles in which a tube is formed from a web of the packaging material usually is provided with an optical reader in a fixed position in view of the so formed tube. For easy access for maintenance and/or replacement, said reader is preferably positioned in a central position in direct opposition to a longitudinal overlap formed during tube forming. Such an optical reader has an effective operational window the width or extent of which is substantially dependent on the distance between the reader and the overlap. To secure a short distance and therefore an accurate optical reading (detection) of the mark said mark should be positioned as close as possible to the overlapping longitudinal edges of the formed tube, which in practice means that said mark shall be positioned within a length not exceeding 20% of the width of the material to form the package from the longitudinal edge thereof, preferably between 5 and 15%. Replacing an optical mark requiring an optical reader with a magnetisable information-carrying mark according to the invention also necessitate a replacement of the former optical reader with a magnetic reader which can be positioned in the same position and by using the already installed supporting means in the filling machine, without requiring any extra cost-demanding installation means.
The magnetic field pattern may comprises at least a first magnetic field peak having a first polarity and a second magnetic field peak having a second opposite polarity. The material may define a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, a longitudinal direction perpendicular to the transversal direction, and an imaginary line between a midpoint of the first peak and the second peak of the magnetic field pattern, wherein the magnetic field pattern may be arranged such that the angle between the imaginary line and the longitudinal direction is between −10 and 10 degrees, preferably between −5 and 5 degrees, preferably about 0 degrees. The peaks of the magnetic pattern may have a distribution forming a substantially constant magnetic field along a width of the magnetic pattern in a direction perpendicular to the imaginary line, and forming a strongly decreasing magnetic field outside the width of the magnetic pattern in the direction perpendicular to the imaginary line. The width may be at least 2 mm, preferably at least 4 mm, preferably at least 6 mm.
According to a further embodiment of the invention different marks are used on the same package. The packaging material comprises a plurality of magnetisable portions thereon comprising at least one detectable magnetisable portion per package to be formed from the packaging material, wherein, per package, at least one of the magnetisable portions provides a first magnetic mark carrying a magnetic field pattern, and another of the magnetisable portions provides a second magnetic mark carrying a magnetic field pattern.
The first magnetic mark is a master mark (register mark) such that operations for finishing the package is enabled to gain information on positioning of the part of the web intended to form the package. A master mark is typically used to position the web of packaging material during processing either during production or later during the forming and filling of packages from the packaging material.
The second magnetic mark is associated with a feature for enhancing finishing of packages such that an operation associated with the feature and to be performed for finishing the package is enabled to gain information on positioning of the part of the web intended to form the package, and/or the first magnetic mark may be associated with a feature for enhancing finishing of packages such that an operation associated with the feature and to be performed for finishing the package is enabled to gain information on positioning of the part of the web intended to form the package.
The magnetic fields of the first and/or second magnetic marks represent complex data. The packaging material defines a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, and a longitudinal direction perpendicular to the transversal direction, wherein at least one of the magnetisable portions may comprise a strip essentially along the longitudinal direction of the web, and the second magnetic mark may be provided by said strip. The complex data may hold information from which the material can be uniquely identified, preferably information from which a part of the material can be uniquely identified. The complex data may be represented as a modulating scheme of the magnetic field of the magnetic pattern, wherein the modulating scheme comprises any of a group comprising phase shift keying, frequency shift keying, amplitude shift keying, quadrature amplitude modulation, and pulse width modulation. The use of multitude of marks per package or a modulation scheme for the data per mark enhances the amount of data available per package without a need for a larger amount of magnetisable material being printed on a layer of the packaging material. This allows for an inexpensive provision of said marks. Furthermore, the print of the magnetisable material can remain the same, but the amount of data per package be increased without substantial investment.
According to another aspect of the invention, there is provided a packaging material comprising a plurality of magnetisable portions thereon comprising at least one detectable magnetisable portion per package to be formed from the packaging material. At least one of the magnetisable portions provides a magnetic mark carrying a magnetic field pattern. The magnetic field pattern comprises a first magnetic field peak having a first polarity and a second magnetic field peak having a second opposite polarity—can be inexpensively magnetised by a permanent magnet. It is advantageous for exact reading and positioning to keep the distance between the peaks low preferably below 20 min, best between 1 and 3 mm.
The packaging material defines a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, a longitudinal direction perpendicular to the transversal direction, and an imaginary line between a midpoint of the first peak and the second peak of the magnetic field pattern, wherein the magnetic field pattern is arranged such that the angle between the imaginary line and the longitudinal direction is between −10 and 10 degrees, preferably between −5 and 5 degrees, preferably about 0 degrees. The peaks of the magnetic pattern have a distribution forming a substantially constant magnetic field along a width of the magnetic pattern in a direction perpendicular to the imaginary line, and forming a strongly decreasing magnetic field outside the width of the magnetic pattern in the direction perpendicular to the imaginary line. The width may be at least 2 mm, preferably at least 4 mm, preferably at least 6 mm. A good detection of the mark in both directions is important for keeping good readability should the web slightly move off-center, but also for adjusting the web in longitudinal direction, orthogonal to the web movement. For the longitudinal direction a mark with a smaller width of the magnetic pattern and/or a sharp edge of the magnetic pattern provide an improved resolution of the. However, a broad magnetic field pattern or a slowly rising edge of said magnetic field pattern secure a better robustness for the reading of the mark.
The second magnetic field peak may be distributed such that it encircles the first peak in the plane of the material and has a second opposite polarity to the first magnetic field peak.
According to another aspect of the invention, there is provided a packaging material comprising a plurality of magnetisable portions thereon comprising at least one detectable magnetisable portion per package to be formed from the packaging material, and at least one preparation feature for enhancing finishing of packages, wherein the at least one preparation feature is aligned with a magnetic field mark in the at least one magnetisable portion.
The preparation feature comprises any of a group comprising crease lines, openings, perforations, package boundary or sealing, beginning of web, end of web, positioning of optical mark, detectable print (décor) on the package. The mark should not interfere with the preparation feature to avoid destruction of the mark during such preparation. The magnetisable portion is produced during an early phase of the production process of the packaging material. A later compression, bending or stretching of the packaging material exactly at the position of the later mark may compromise its quality.
According to further improvement of the invention, the distance between an area of the preparation feature and its aligned magnetic field mark may be at least 2 mm, preferably at least 5 mm, preferably at least 7 mm, preferably at least 10 mm. Portion packages have a limited surface, but also the highest speeds in the filling machine. Large distances secure good marks and few reading errors; smaller distances can be used with more elaborate package shapes and additional functionality on the package.
At least one of the magnetic marks for each package to be formed may be positioned not more than 20%, preferably between 5 and 15% of the width of the material to form a package from a longitudinal edge of the material to form the package. The reason is that a conventional filling machine used to manufacture a packaging container according to forming/filling/sealing principles in which a tube is formed from a web of the packaging material usually is provided with an optical reader in a fixed position in view of the so formed tube. For easy access for maintenance and/or replacement, said reader is preferably positioned in a central position in direct opposition to a longitudinal overlap formed during tube forming. Such an optical reader has an effective operational window the width or extent of which is substantially dependent on the distance between the reader and the overlap. To secure a short distance and therefore an accurate optical reading (detection) of the mark said mark should be positioned as close as possible to the overlapping longitudinal edges of the formed tube, which in practice means that said mark shall be positioned within a length not exceeding 20% of the width of the material to form the package from the longitudinal edge thereof, preferably between 5 and 15%. Replacing an optical mark requiring an optical reader with a magnetisable information-carrying mark according to the invention also necessitate a replacement of the former optical reader with a magnetic reader which can be positioned in the same position and by using the already installed supporting means in the filling machine, without requiring any extra cost-demanding installation means.
According to another aspect of the invention, there is provided a packaging material comprising a plurality of magnetisable portions thereon, being provided as at least one detectable magnetisable portion per package to be formed from the packaging material, the detectable magnetisable portions comprising magnetisable particles.
The detectable magnetisable portion may be essentially of a geometrical shape chosen from the group consisting of rectangular, square, circular, oval and elongated shape. At least one of the detectable magnetisable portions may be intended for magnetic position marking and may have an area less than 250 mm2, preferably less than 150 mm2, preferably less than 25 mm2. Smaller detectable magnetisable portions requires less magnetisable particle in production, but higher precision at the step to magnetise the particles during production. Larger detectable magnetisable portions are more forgiving during magnetisation and do not necessitate the same quality of alignment of the web during production.
The width of the magnetic mark is related to the magnetic reader, see WO2006093449 A1 for an exhaustive description of a reader which could be used. Potentially many of such readers are used in a single filling machine. Small compact readers are needed to be used in the filling machine to support the package production as a register control (position the web for cap application, sealing or cutting), tube twisting correction or splicing. There is little space available in the filling machine to mount the readers. Small but robust magnetic marks are preferable. Some, but not too much extra surface is given to the magnetisable portions onto which the magnetisation will be performed to produce the magnetic mark.
The detectable magnetisable portions may comprise magnetisable particles of an amount between 0.5 and 4 g per m2 print area, preferably between 1.5 and 4 g per m2, preferably about 2 g per m2.
The packaging material defines a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, and a longitudinal direction perpendicular to the transversal direction, wherein at least one of the magnetisable portions may comprise a strip essentially along the longitudinal direction of the web. The strip comprise piecewise divided parts, wherein one part is present for each package to be formed from the packing material. A division between the parts may be positioned such that sealing of the package to be formed from the packing material is enabled at the position of the division. The strip may comprise a magnetic mark indicating a predetermined distance to the intended position of sealing. The strip is furthermore the preferable location of any other mark containing information relating to the packaging material, it's composition, it's intended purpose or ordering entity.
The detectable magnetisable portions may be provided as prints which are made by magnetisable ink comprising magnetisable particles, a solvent and a binder. The magnetisable particles may by chosen from the group consisting of maghemite and hematite. The binder may be chosen from the group consisting of acrylate, acrylics such as styrene acrylic copolymer, polyurethane, nitrocellulose, polyamide and latex. The binder may comprise two of the group, wherein one serves as a disperant such that the magnetisable particles are evenly dispersed in the ink and the other serves as an adhesive to the packaging material. The amount of binder may be between 20 and 60 percent of weight of the ink, preferably between 40 and 60 percent, preferably between 50 and 55 percent. The ink may further comprise additives, such as waxes and/or antifoaming agent. The waxes may comprise any of a group comprising polyethylene, polypropylene, silicone, polyamide, ethylene vinyl acetate, ethylene butyl acetate, ethylene acrylic acid and polytetrafluoro ethylene. The antifoaming agent may comprise silicone or mineral oil. The solvent may comprise any of a group comprising ethanol, ethylic acetate, water, iso-propanol, glycol, or a retarder solvent. The amount of magnetisable particles may be between 15 and 40 percent by weight of the ink, preferably 30-35 percent by weight. The size of the magnetisable particles may be between 0.1 and 2.5 μm, preferably between 0.1 and 0.8 μm or preferably between 0.4 and 1.5 μm, preferably about 0.3 μm or preferably about 1 μm.
According to another embodiment of the invention the packaging material comprises a plurality of magnetisable portions of magnetisable particles being provided on the side of the paper layer intended to face towards the interior of the package. The magnetisable portions are typically of a dark colour. Inside print will reduce the visibility of the detectable magnetisable portions or amount of whitening substances being introduce into the packaging material.
The packaging material comprises a layer of paper and a layer of plastic coating, and the detectable magnetisable portions are provided on the layer of paper. The at least one detectable magnetisable portion may be printed on the side of the paper layer intended to face to the interior of the package. The laminate comprises further a metal foil layer of a non-ferromagnetic metal such that the magnetisable portion is electromagnetically accessible through the metal foil. Due to that choice no negative influence of the metal foil on the magnetisation will be observed.
The prints may be made by a magnetisable ink comprising magnetisable particles, a solvent and a binder. The magnetisable particles may be chosen from the group consisting of magnetite and maghemite. The binder may be chosen from the group consisting of acrylate, acrylics such as styrene acrylic copolymer, polyurethane, nitrocellulose, polyamide and latex. The binder may comprise two of the group, wherein one serves as a dispersant such that the magnetisable particles are evenly dispersed in the ink and the other serves as an adhesive to the packaging material. The amount of binder may be between 20 and 60 percent of weight of the ink, preferably between 40 and 60 percent, preferably between 50 and 55 percent. The ink may further comprise additives, such as waxes and/or antifoaming agent. The waxes may comprise any of a group comprising polyethylene, polypropylene, silicone, polyamide, ethylene vinyl acetate, ethylene butyl acetate, ethylene acrylic acid and polytetrafluoro ethylene. The antifoaming agent may comprise silicone or mineral oil. The solvent may comprise any of a group comprising ethanol, ethylic acetate, water, iso-propanol, glycol, or a retarder solvent. The amount of magnetisable particles may be between 15 and 40 percent by weight of the ink, preferably 30-35 percent by weight. The size of the magnetisable particles may be between 0.1 and 2.5 μm, preferably between 0.1 and 0.8 μm or preferably between 0.4 and 1.5 μm, preferably about 0.3 μm or preferably about 1 μm.
According to a first aspect, there is provided a magnetisable ink suitable for a packing material for forming food packages, comprising magnetisable particles; a solvent; and a binder.
In a preferred embodiment the magnetisable ink is adapted for high speed printing of a web of a packaging material comprising a base layer of paper or paperboard, in which said magnetisable ink is suitable for printing directly on the paper or paperboard layer. In particular, said magnetisable ink is adapted to be printed on the surface of said paper or paperboard layer which is intended to be facing towards the interior of a food package manufactured from said packaging material. The magnetisable particles may be chosen from the group consisting of maghemite and hematite.
The binder may be chosen from the group consisting of acrylate, acrylics such as styrene acrylic copolymer, polyurethane, nitrocellulose, polyamide and latex. The binder may comprise two of the group, wherein one serves as a dispersant such that the magnetisable particles are evenly dispersed in the ink and the other serves as an adhesive to the material. The amount of binder may be between 20 and 60 percent of weight of the ink, preferably between 40 and 60 percent, preferably between 50 and 55 percent.
The magnetisable ink may further comprise additives, such as waxes and/or antifoaming agent. The waxes may comprise any of a group comprising carnauba, paraffin, polyethylene, polypropylene, silicone, polyamide, ethylene vinyl acetate, ethylene butyl acetate, ethylene acrylic acid and polytetrafluoro ethylene. The antifoaming agent may comprise polyglycol, mineral oil, polysiloxanes, hydrophobic silica, silicone or mineral oil. The solvent may comprise any of a group comprising ethoxy propanol, n-propanol, ethanol, ethylic acetate, water, iso-propanol, glycol, or a retarder solvent. The amount of magnetisable particles may be between 15 and 40 percent by weight of the ink, preferably 30-35 percent by weight.
The size of the magnetisable particles may be between 0.1 and 2.5 μm, preferably between 0.1 and 0.8 μm or preferably between 0.4 and 1.5 μm, preferably about 0.3 μm or preferably about 1 μm.
Applications
The improved packaging material can be applied in the filling machine to enable additional machine functions or to improve the precision of machine function thereby improving the quality and appearance of the produced package and reducing waste.
A packaging material comprises according to a further embodiment of the invention a plurality of magnetisable portions with at least one detectable magnetisable portion per package to be formed from the packaging material The detectable magnetisable portions comprising magnetisable particles, wherein at least one of the magnetisable portions provides a magnetic mark carrying a magnetic field pattern enabling position determination such that upon splicing a first and a second web of such material, the first and second webs are enabled to be aligned by using determined positions from respective web. Splices between two reels of packaging material can be executed with high precision and minimal waste. The marks for improved splicing can be generated only at the ends of a web of the material or periodically throughout the web.
Furthermore, defining a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, and a longitudinal direction perpendicular to the transversal direction, wherein the alignment of the webs in the longitudinal direction is based on the periodicity of the packages to be formed from the packaging material and the determined position information. Using multiple marks for positioning the web further improves the precision.
The invention can be advantageously be used in the filling machine to detect and correct the twisting of the tube of web-like packaging material before sealing and cutting. A web-like packaging material to be reformed into a tube to be sealed at one end, filled with content, sealed again to enclose the content, cut, and formed to a package, comprises a plurality of magnetisable portions. During production of the packaging material at least one magnetic mark is created per package to be formed from the packaging material. One or more of these magnetisable portions provide a first magnetic mark carrying a magnetic field pattern with accurate position information through which any twist of the formed tube can be detected and corrected.
According to another improvement, the positioning of the mark on the web allows for high precision control of the web during operations with varying web speeds. The packaging material comprises a plurality of magnetic marks printed with at least one magnetic mark per package to be formed from the packaging material. Said at least one magnetic mark is aligned with a preparation feature associated with an operation to be made to finish packages. One magnetic mark is positioned on the material such that relative speed between the material and means for reading the magnetic mark is not zero, but also well below the maximum speed the web might reach in the filling machine. The relative speed in an indexing operation varies between zero and a relatively high speed during the production of portion packages in a high speed filling machine which can produce up to 24.000 packages per hour. The reader is fixed in the filling machine at a given position relative to the work station which is in operation once the web is stopped. The mark is advantageously positioned at the web at positions which correspond to the reader position where the web passes at low speeds.
In one embodiment of the invention there is provided a packaging material comprising a magnetic mark providing a magnetic field pattern and being aligned with an operation for applying an opening device on the packaging material, wherein said magnetic mark is positioned on the material such that relative speed between the material and reader is low and preferably substantially constant.
The magnetic field pattern may comprise a first magnetic field peak having a first polarity and a second magnetic field peak having a second opposite polarity. The material may define a transversal direction being parallel to an imaginary axis of a roll when a web of the material is spooled, a longitudinal direction perpendicular to the transversal direction, and an imaginary line between a midpoint of the first peak and the second peak of the magnetic field pattern, wherein the magnetic field pattern may be arranged such that the angle between the imaginary line and the longitudinal direction is between −10 and 10 degrees, preferably between −5 and 5 degrees, preferably about 0 degrees. The peaks of the magnetic pattern may have a distribution forming a substantially constant magnetic field along a width of the magnetic pattern in a direction perpendicular to the imaginary line, and forming a strongly decreasing magnetic field outside the width of the magnetic pattern in the direction perpendicular to the imaginary line. The width may be at least 2 mm, preferably at least 4 mm, preferably at least 6 mm. To be able to combine this advantageous embodiment of the mark and its position with other application, the magnetic field pattern may comprise a first magnetic field peak having a first polarity and a second magnetic field peak being distributed such that it encircles the first peak and having a second opposite polarity.
The relative speed shall be zero at writing of the magnetic mark, and may be non-zero at reading of the magnetic mark. Thus, at writing of the magnetic mark, there is no slip between the writing means and the packaging material (as it is the case in a roller which provides the packaging material with crease lines), which implies that the magnetic mark is accurately assigned. At reading of the magnetic mark, there is a movement between the reading means and the magnetic mark should be such that the pattern of the magnetic mark can be properly detected. In case where the packaging material is intended for manufacturing of packages by means of a filling machine operating in an indexing manner said at least one magnetic mark is preferably located on the packaging material such that it is detected when the travelling speed of the packaging material is below 50% of its maximum value to obtain a good detection of the magnetic mark.
According to a further improvement, the mark is used by a method to adjust and position the web moving at various speeds, as it is the case if the web is moved and stopped in indexing activities. The method comprises controlling a relative speed between reading means and the material to be non-zero. Preferably, the relative speed between the reading means and the packaging material is controlled to be below 50% of its maximum value in case the packaging material is traveling in a cycling or indexing manner through a packaging machine of the kind which forms, fills and seals packages in a continuous manner from the packaging material passing therethrough. The controlling of the relative speed may comprise providing a slacking portion of the material both before and after the reading position such that speed at the writing position is enabled to be constant at instant of reading irrespective of general speed variations of the material.
The magnetic field of the magnetic marks needs to be strong enough to be read with robustness, but is also low, preferably in the range of 90-240 MSS. Having such field strength the magnetic mark will not be permanently altered by magnetic field disturbances <1000 μT.
Maximum magnetic field fluctuations from one magnetic mark to the next one are within +/−15 MSS within a packaging material. MSS is a unit of magnetic field strength measured as the parallel magnetic field 0.7 mm apart from the centre of a magnetic mark at the mark's side facing towards its magnetisation. The measurement value is related to the test method I025.307. That low field strength is securing a minimum impact on the food filled into the package and the working environing during production of the packaging material and the package.